The overall objective of this project is to provide a better understanding of the molecular mechanisms underlying cellular movements essential for normal development. Our working hypothesis is that some congenital malformations such as neural tube defects may arise from either defects in the cytoplasmic contractile system that is involved in cell movements or from teratogenic insults which disrupt this sytem at a crucial time. It is proposed to undertake an immunochemical approach to the analysis of actin, a major contractile element. Specifically, it is proposed to develop monoclonal antibodies against the cytoplasmic and muscle actins. Emphasis will be placed on genrating antibodies that are specific for each of the six known isoactins; highest priority will be given to the cytoplasmic actin forms. The hybridoma antibodies as well as rabbit and hybridoma antibodies that are already available in this laboratory will be used to localize actin the neuroepithelial cells found in fusing and non-fusing regions of the neural fold in the same embryo as well as in embryos of different developmental stages. Both indirect immunofluorescent and microscopic studies will be employed. These antibodies also will be used to define the antigenic, structural and functional relationships among the isoactins. This will include assessing the complexity of antigenic changes associated with the known amino acid substitutions among the isoactins; assessing the relationship between each antibody binding site and functional sites in the actins by determining the effects of these antibodies on actin polymerization, gelation, activation of myosin ATPase, and binding of accessory proteins; and assessing the effects of actin antibodies on movements of cells in tissue culture such as migration, division, attachment, chemotaxis, neurite extension and membrane ruffling. Antibodies will be delivered by either direct microinjection or via loaded red cell ghosts.